1. Field of the Invention
The present invention relates to an image processing unit, or more particularly, to an image processing unit characterized by its expansion facilities for processing an endoscopic picture.
2. Description of the Related Art
In recent years, endoscopic imaging systems have widely prevailed. An insertion unit of such an endoscopic imaging system is inserted into a region to be observed in a body cavity. Illumination light is propagated using an illumination light propagating means such as a light guide fiber bundle, and irradiated from the distal end of the insertion unit to the region to be observed. A picture of the region to be observed is thus produced and used to observe or treat the region to be observed.
The endoscopic imaging systems include an electronic endoscopic imaging system having a solid-state imaging device, for example, a CCD incorporated in the distal part of an insertion unit thereof. An optical image of a region to be observed is formed on the image plane of an objective optical system, converted into an electric signal. The electric signal is processed in order to display images of the region to be observed on a monitor or the like, or to store image data in an information recording unit or the like.
For example, in the department of surgery, a rigid endoscopic imaging system for surgical use is available. A rigid insertion unit of a rigid endoscope is inserted into a region to be observed in a body cavity. Illumination light is propagated using an illumination light propagating means and irradiated to the region to be observed through the distal end of the insertion unit. An optical image of the region to be observed is propagated from the distal end of the insertion unit to an eyepiece unit using an image propagating means such as relay lenses. A CCD incorporated in an external TV camera, which is mounted on the eyepiece unit so that it can be dismounted freely, produces images of the region to be observed. The images of the region to be observed are displayed on a monitor or the like. With the help of the images, surgery is carried out.
As far as a typical endoscopic imaging system is concerned, endoscopic images are displayed on a monitor or the like. With the help of the endoscopic images, diagnosis or the like is carried out. A demand made for a way of processing the endoscopic images varies depending on a department or a purpose of use.
Specifically, in the department of surgery, there is an increasing demand for simply displaying endoscopic images as a motion picture on a monitor or the like. In contrast, in the department of otorhinology, there is a demand for observing endoscopic images as still images and preserving the still images as digital image data.
A camera control unit (CCU) serving as an image processing unit included in a conventional endoscopic imaging system is provided with a facility for producing still images or processing a digital image output in efforts to satisfy the demands.
An endoscopic imaging system for surgical use is requested to display endoscopic images as a motion picture on a monitor or the like. Nevertheless, the endoscopic imaging system is demanded to be usable in multiple departments or for multiple purposes of use. Therefore, a CCD must be provided with many facilities including a facility for producing still images and a facility for processing a digital image output. Many types of CCUs must be included in line with the purposes of use. Furthermore, dedicated peripheral equipment may be needed. The endoscopic imaging system cannot therefore be constructed inexpensively.
Even in the department of surgery, a way of displaying endoscopic images as a motion picture may vary depending on an operator. Specifically, some operators may want to view the motion picture vertically inverted or laterally inverted. For meeting this demand, as far as the conventional CCU is concerned, a dedicated processing circuit for inverting a motion picture vertically or laterally must be installed in the CCU in advance. The endoscopic imaging system cannot therefore be constructed inexpensively.
In the conventional endoscopic imaging system, an analog VTR and a high-image quality video tape are used to record a motion picture. An operator uses the VTR to reproduce the motion picture from the recorded video tape, and creates a video or slides for use at meetings of organizations. Another person may capture still images to be appended to a clinical recording if necessary or to be given to a patient. Otherwise, a view picture may be reproduced immediately after diagnosis in order to explain a patient's symptom while showing the picture to the patient.
A picture recorded using the analog VTR and high-image quality video tape in combination exhibits a limit resolution of approximately 400 scanning lines. In contrast, when a high-resolution soft endoscope and a single-plate camera are used in combination, 480 scanning lines are traced in order to display an image on a display screen of a monitor included in an endoscopic imaging system. A combination of a high-resolution rigid endoscope and a single-plate camera permits a maximum of 750 scanning lines to be traced in order to display an image on the display screen of the monitor included in the endoscopic imaging system. The image quality provided by the VTR is lower than the image quality of images displayed on the display screen of the monitor. This poses a problem in that what is displayed on the display screen of the monitor during surgery or diagnosis is indiscernible from images reproduced by the VTR.
In recent years, a digital video (DV) compression type digital VTR permitting recording with higher image quality than the image quality of images recorded using the combination of an analog VTR and high-image quality video tape has begun to prevail. Furthermore, the MPEG2 standard adopted as a compression format according to which a video signal used for digital broadcasting or in DVD videos is compressed is attracting attention.
Digital media including a digital video cassette tape having a width of 6 mm, a DVD ROM, and a DVD RAM enables, as mentioned above, higher-image quality recording than conventional analog media. Besides, the volume of a medium used for recording is smaller. This contributes to the preservation of space in a hospital. The digital media is therefore attracting great attention. The aforesaid DV recording technique permits recording of data read with up to 500 scanning lines. The 500 scanning lines covers the limit resolution offered by the single-plate camera that occupies a large share in the market of endoscopes.
Japanese Unexamined Patent Application Publication No. 10-286231 has disclosed an electronic endoscopic imaging system having a video processing unit. The video processing unit produces a digital video signal, which can be structured in conformity with a plurality of formats, using a video signal output from a solid-state imaging device. Consequently, a signal can be transmitted to a plurality of pieces of peripheral equipment including a display device without any deterioration.
However, an endoscopic imaging system is a relatively expensive system to be purchased by a hospital. Now that any digital motion picture recording format has not yet been standardized, if an endoscopic imaging system is purchased, the output format for a digital motion picture adopted in the system may not be interchangeable with another format which may be standardized in the future. Consequently, the endoscopic imaging system may be expensive but incompatible with any future standard.